The utility model discloses a membrane bioreactor (MBR) device comprising a raw water tank, an MBR reaction tank and a clear water tank which are sequentially connected, wherein the top of the MBR reaction tank is fixedly provided with a horizontal cover net, and the bottom of the MBR reaction tank is provided with a horizontal compression net which can vertically move and is provided with an ultrafiltration membrane assembly reserved hole in the middle; polyurethane sponge filler is filled between the horizontal cover net and the horizontal compression net; the filler is simultaneously shrunk to the top when the horizontal compression net is shrunk to the top of the reaction tank, so that the condition that a micropopulation in the filler is destroyed by back flushing is avoided; polyurethane sponge is of a porous structure, can provide a carrier for the growth of microorganisms and can be simultaneously suitable for the attached growth of anaerobic and aerobic microorganisms, so that the nitrification and denitrification effects are improved, and the nitrogen removal rate is increased; due to the existence of the filler, the concentration of activated sludge in the reaction tank can be effectively reduced, the concentration of microorganisms in a mixed liquid can be reduced, and the pollution to an ultrafiltration membrane can be delayed; a main pipeline is also provided with two back flushing pipelines, so that the same pump is used in the back flushing and water discharging processes, and furthermore, the equipment cost is reduced; and the MBR device is widely applied to treatment of urban sewage and industrial wastewater and particularly to the treatment of high-concentration ammonia-nitrogen wastewater.